High-frequency induction heating coil



April 12, 1949. R. D. FRAZIER 2,467,201

HIGH-FREQUENCY INDUCTION HEATING COIL Filed June 18, 1945 i Attorney.

v Varlf Patented Apr. 12, 1949 UNlTED HIGH-FREQUENCY INDUCTION HEATINGCOIL Richard D. Frazier, Schenectady, N. Y., assignor to GeneralElectric Company, a corporation of New York Application June 18, 1945,Serial No. 600,038

2 Claims. 1

My invention relates to high frequency heating coils and has for itsobject a simple and efiicient coil for heating convex or concavesurfaces.

More particularly, my invention relates to the heating of metal partsfor surface hardening purposes by high frequency currents having frequencies up to 500,000 cycles a second or more. It is more specificallydirected to the surface heating of metal articles passed continuously inheating relation with the coil, the article having a convex or concavesurface to be heated.

In carrying out my invention in one form I provide a fiat spiral orpancake coil bent or shaped to fit the concave or convex surface to beheated.

For a more complete understanding of my invention reference should behad to the accompanying drawing, Fig. 1 of which is a fragmentary sideelevation view of a high frequency heating coil embodying my inventionapplied to the heating of the beveled edge of a metal bar. Fig. 2 is anend elevation view of the apparatus shown in Fig. 1. Fig. 3 is a viewsimilar to Fig. 1 showing a coil embodying m invention for heating theconcave edge of a metal bar. Fig. 4; is an end view of Fig. 3, whileFig. 5 is a plan view of Fig. 3.

Referring to the drawing, I have shown my invention in one form in Figs.1 and 2 as applied to the heating of the upper convex edge 5 of a steelbar 2, the edge I being beveled or pointed as seen in Fig. 2 with twoplane surfaces positioned at an acute angle with each other.

For heating the upper edge I, I provide a coil 3 which is wound in theform of a fiat spiral coil and then bent along a diameter into two flatside portions 5 and 0, having substantially the same angular relation asthe sides of the beveled edge I. This coil is mounted on a suitableelectrically insulating support, not shown, to provide for the passageof the steel bar 2 under the coil, as shown in the drawing, with the twosides of the edge I in equally spaced substantially parallel relationwith the two flat portions 5 and 6 of the coil.

During the heating operation the bar 2 is moved by suitable conveyormeans, not shown, continuously at a predetermined speed from the righttoward the left as seen in Fig. 1 and as indicated by the arrow I, whilethe coil 3 is en ergized from a suitable source of high frequencycurrent supply, the terminals of which are connected to the terminals 8and 9 of the coil. This source of high frequency current preferably isan electronic tube oscillation generator supplying current having afrequency of 500,000 cycles a second or more. The rate of movement ofthe bar 2 is adjusted relative to the rate of heating in such mannerthat when the bar is moved continuously at the predetermined speed themetal on the sides of the beveled portion I to a predetermined depth isheated to the decalescent or hardening temperature of the metal inpassing along the coil.

As the heated portion of the bar moves out from under the coil it isimmediately quenched to harden it by the application of a suitablecooling liquid such as water from a quenching device I0. This deviceconsists of a U-shaped container having suitable apertures, not shown,in its in- I side wall. Water is supplied at a suitable pressure to thiscontainer I0 and is forced through the apertures onto the bar 2 therebyquickly to cool the metal of the beveled portion and harden it. For thepurpose of providing a sharp line of demarcation for the quenching waterthereby preventing the application of the water to the heating coil andthe portion of the bar being heated, a baffle wall I I is providedtogether with a nozzle I2 for applying water to the side of the baffleopposite the heating coil. The water from the nozzle I2 flows down theouter side of the bafile II, the lower end of which is closely adjacentthe beveled edge I and then onto the beveled edge, thereby to provide aninitial cooling and hardening immediately after the heated beveled edgeleaves the coil. The cooling is completed by the quench device I0.

Referring to Figs. 3, 4 and 5 in this application of my invention thesteel bar It is provided with a concave upper edge I4 forming alongitudinal V-shaped notch in the edge of the bar with two planesurfaces positioned at an acute angle with each other. In the heating ofthis concave edge I have provided a coil I5 which is provided with twoflat sides or portions I0 and I1 positioned at an angle with each othersubstantially the same as the angle between the surfaces of the notchI4. As shown clearly in Fig. 5, this coil consists in effect of tworeversely wound elongated pancake or spiral coils. Thus, starting fromthe inner terminal I8 the conductor extends counterclockwise to form aplurality of substantially straight parallel lengths up to and includinga central length I9 at the end of which the conductor is wound clockwisein a similar number of substantially parallel loops to the oppositeinner terminal 20 of the coil.

As shown in the drawing the coil I5 is positioned by electricallyinsulating supporting means, not shown, with the central length I 9 fthe coil adjacent the lowest point of the edge of the bar, i. e.opposite the junction of the two flat sides of the V-shaped notch andwith the two portions it and I1 in equally spaced parallel relation withthe sides of the notch.

In the operation of the apparatus, shown in Figs, 3, 4 and 5, the bar ismoved from the righthand toward the left-hand in the direction of thearrow 2| of Fig. 3 at a predetermined speed, the

coil being energized with high frequency current having a frequency of500,000 cycles a second or more. The bar is cooled after leaving thecoil by water supplied by two nozzles 22 and 23 and a quenching device24. The nozzles 22 and 23 are positioned at an acute angle with respectto each other to direct the flow of cooling water along the two planesurfaces of the V-shaped edge of the bar, Preferably the bar I3 ispositioned with its left-hand end somewhat lower than its righthand endso that the cooling water flows in the V-shaped notch toward the leftaway from the coil and the portion being heated.

It will be observed that this reversely wound double pancake coilprovides a plurality of substantially parallel straight side by sideconductors at the center in which the current flows in the samedirection. In the coil shown the two pairs of conductors 25 and 20, onopposite sides of the central conductor ill at the apex of the anglebetween the portions IB and I1, carry current flowing in the samedirection as in the central conductor i9. This provides for the maximummagnetic flux in the walls of the notch and maximum heating eifect.While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto, sincemany modifications may be made, and I therefore contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A high frequency heating coil comprising a continuous electricconductor shaped into two reversely wound flat spiral coils having aplurality of substantially parallel side by side adjacent conductorsforming adjacent sides of said coils in which a current in saidconductor flows in the same direction, said coils being connectedtogether by a central one of said parallel conductors.

2. A high frequency heating coil for heating a body having nonparallelintersecting surfaces comprising a continuous electric conductor shapedinto two elongated reversely wound flat spiral coils having a pluralityof substantially parallel straight side by side conductors adjacent eachother in which a current in said conductor flows in the same direction,said coils being positioned in nonparallel relation with each other andconnected together by a central one of said parallel conductors.

RICHARD D. FRAZIE-R.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,052,010 Bailey Aug. 25, 19362,075,079 Anderson Mar. 30, 1937 2,118,594 Douden May 24, 19382,14%,3'18 Kennedy Jan. 17, 1939 2,270,293 Grunder Jan. 20, 19422,308,240 Goodridge Jan. 12, 1943 FOREIGN PATENTS Number Country Date541,155 Germany Jan. 11, 1932 OTHER REFERENCES Babat, Heat Treating andForging, March 1941, pages 137, 138, and 139.

Electronics, October 1943, pages 112, 113, 299, and 300.

